To investigate the nm-size dependence of structural and thermal properties for AgI, the formation of composites between AgI
and porous silica with controlled pore diameters of 10, 15, 30, and 50 nm was examined. The introduction of AgI within the
micropores of the porous silica was performed successfully by a salt-bridge precipitation method with using AgNO3 and KI aqueous solutions. The AgI formed within the micropores was identified to be β/γ-AgI, independent of the pore size
of 10-50 nm, by powder X-ray diffractometry. In differential scanning calorimetry, the composites showed thermal anomaly at
around 150C on heating due to the phase transition from β/γ -AgI to α -AgI as in the case of bulk crystalline AgI (Ttrs=147C). However, the transition temperature from α-AgI to β/γ -AgI on cooling decreased remarkably with the decrease of the
pore size from 50 to 10 nm. The result indicates the possibility for AgI particles with diameter less than 10 nm to exist
as α -AgI even below 100C.
The compound BR-A657 is an angiotensin II receptor antagonist. The objective of this work was to investigate the existence
of polymorphs and pseudopolymorphs of BR-A657 and the transformation of crystal forms. Three crystal forms of BR-A657 have
been isolated by recrystallization and characterized by powder X-ray diffractometry, differential scanning calorimetry, and
thermogravimetric analysis. After storage of three days at 0% RH (silica gel, 20°C), 52% RH (saturated solution of Na2Cr2O7·2H2O/20°C) and 95% RH (saturated solution of Na2HPO4/20°C), Forms 2 and 3 were transformed to Form 1.
In this work, thermoanalytical, diffractometry, and microscopy measurements have been performed in order to characterize the effect of high energy milling on a drug active in the migraine prophylaxis and smoke cessation. We can assert that the mechanical treatment induces only a partial amorphisation of the solid phase, in particular it reduces the crystal order by producing lattice defects which propagate from the surface to the bulk crystal. For this reason, the DSC is able to detect the presence of ordered solid, while the powder X-ray diffractometry, because of its low penetration depth, does not reach the crystalline core of the particles.
Authors:R. Pena, A. Chauvet, J. Masse, J. Ribet, and J. Maurel
The physicochemical characterization of the solid-state enantiomers and racemate of efaroxan hydrochloride (C13H17N2O+Cl-,
M=252.5 g mol-1) was performed by thermoanalytical methods (differential scanning calorimetry, thermogravimetry and thermomicroscopy)
and spectral methods (infrared spectrometry and X-ray diffractometry).
The efaroxan enantiomers and racemate were shown to be unstable near the melting point. At the beginning of the decomposition,
a loss of hydrogen chloride was observed. However when sealed pans were used, the compounds decomposed at higher temperature,
allowing a precise evaluation of the melting enthalpies by means of differential scanning calorimetry. The nature of the racemate
and its thermal stability were assessed by evaluating its free formation enthalpy. An enantiotropic solid-solid transformation
(II→I) was noted for the racemate; the reverse process (I→II) follows zero-order kinetics.
The aim of this study was to evaluate the drug-polymer interaction in polymeric microsphere formulations containing diltiazem
hydrochloride (DH). The microspheres were successfully prepared by solvent evaporation technique using two different polymer
types, Eudragit®RS 100 and ethylcellulose. The existence of a possible interaction between DH and the polymers was investigated
by using DSC and XRD. The DSC curves and XRD patterns indicated that there was no interaction between DH and the polymers.
The peak area calculations in the DSC curves of F1- and F2-coded microsphere formulations showed that DH was dispersed, not
dissolved, in the ethylcellulose polymer matrix, while it partly dissolved in the Eudragit®RS 100 polymer matrix.
Authors:L. Zhou, J. Sirithunyalug, E. Yonemochi, T. Oguchi, and K. Yamamoto
The interaction between erythritol and 4-hexylresorcinol during heating was investigated by thermal analysis, powder X-ray
diffractometry and infrared spectroscopy. A phase diagram was constructed by measuring the thermal behaviour of various resolidified
physical mixtures of erythritol and 4-hexylresorcinol. The phase diagram revealed complex formation between erythritol and
4-hexylresorcinol with incongruent melting at 84C; the stoichiometry was a molar raio of 1:2 erythritol:4-hexylresorcinol.
The complex gave diffraction peaks at 2θ=5.6 and 11.2 in the X-ray powder diffraction pattern. In the infrared spectrum,
a new peak due to the complex was observed at 3504 cm–1. The complex prepared by grinding and evaporation had the same molecular arrangement as the complex prepared by sealed heating.
DA-5018 is a new capsaicin derivative and has analgesic effect. The objective of this work was to investigate the existence
of polymorphs and pseudopolymorphs of DA-5018 and the transformation of crystal forms. Eight crystal forms of DA-5018 have
been isolated by recrystallization and characterized by powder X-ray diffractometry (PXRD), differential scanning calorimetry
(DSC), and thermogravimetric analysis (TG).
The PXRD and DSC patterns of the eight crystal forms were different respectively.
In the dissolution studies in simulated intestinal fluid at 37±0.5°C, the solubility of Form 2 was the highest. And the solubility
in water decreased in rank order: Form 2>Form 3>Form 1>Form 5>Form 7>Form 4>Form 6>Form 8.
Eight crystal forms were shown to have a good physical stability at room temperature for 60 days.
Polymorphic transitions of α-phenylcinnamic acid stereoisomers crystallized from various solvents (CHCl3, ethanol, diethyl
ether), precipitated with different acids (acetic acid or HCl) or sublimed have been studied by differential scanning calorimetry
(DSC). Measurements were also supplemented by powder X-ray diffractometry (XRD). Polymorphic transitions were not found for
any of the E isomer samples irrespective of the method of treatment. However, in heating-cooling cycles reversible transitions
could be detected for the Z isomer. On heating an exothermic peak was registered on samples sublimed, crystallized from ethanol
or diethyl ether before melting, while samples precipitated by HCl or crystallized from chloroform exhibited more complex
transitions. Here, endothermic effects were also observed. Enthalpy values for transformations (either for melting or polymorphic
and other transitions) are also given.
The reaction process of the thermal dehydration of dilithium tetraborate trihydrate, Li2B4O7
3H2O, was reinvestigated from a viewpoint of reaction kinetics. On the basis of the results of thermogravimetry, constant rate thermal analysis, powder X-ray diffractometry, infrared spectroscopy and scanning electron microscopy, it was confirmed that the reaction proceeds via three consecutive kinetic steps characterized by different activation energies. The first and second kinetic steps, accompanied by the destruction of the original crystal structure of the reactant, seem to be assigned to the surface and internal reactions, respectively. During the third kinetic step, the thermal dehydration of hydrated amorphous intermediate, produced at the second kinetic step, and crystallization of the final dehydration product, Li2B4O7, are likely to take place concurrently.
Authors:A. Schmidt, V. Niederwanger, and U. Griesser
Two polymorphic forms, a dioxane solvate and the amorphous form of the local anaesthetic drug prilocaine hydrochloride (N-(2-methylphenyl)-2-propylamino
monohydrochloride, PRCHC) were characterized by thermal analysis (hot stage microscopy, differential scanning calorimetry,
thermogravimetry), vibrational spectroscopy (FTIR, FT-Raman-spectroscopy), powder X-ray diffractometry and water vapor sorption
analysis. The formation and thermodynamic stability of the different solid phases is described and presented in a flow chart
and an energy temperature diagram, respectively. Mod. I (m.p. 169C) is the thermodynamically stable form at room temperature and present in commercial products. This form crystallizes
from all tested solvents except 1,4-dioxane which gives a solvate with half a mole of 1,4-dioxane per mole PRCHC. Mod. II
occurs only on desolvation of the dioxane solvate and shows a lower melting point (165.5C) than mod. I and a lower heat
of fusion. Thus, according to the heat of fusion rule, mod. II is the thermodynamically less stable form in the entire temperature
range (monotropism) but kinetically stable for at least a year. Freeze-drying of an aqueous solution leads to the amorphous
form. On heating and in moist air amorphous PRCHC exclusively crystallizes to the stable mod. I. PRCHC exemplifies that certain
metastable polymorphic forms are only accessible via a specific solvate, but not via any other crystallization path. Since
no crystallization from 1,4-dioxane was performed in earlier solid-state studies of this compound, PRCHC was to this date
rated as monomorphic.